The present invention relates generally to memory cards, and more particularly to a memory card (e.g., a multi-media card or secure digital card) comprising a semiconductor device module which is configured to be interfaced to an external case in manner maintaining prescribed tolerances between the module and the case, and preventing undesirable adhesive leakage from within a cavity of the case into which the module is advanced.
As is well known in the electronics industry, memory cards are being used in increasing numbers to provide memory storage and other electronic functions for devices such as digital cameras, MP3 players, cellular phones, and personal digital assistants. In this regard, memory cards are provided in various formats, including multi-media cards and secure digital cards.
Many memory cards include a module which itself comprises a printed circuit board (PCB) having a conductive wiring pattern disposed thereon. Attached to one side or surface of the PCB and electrically connected to the conductive pattern thereof is a plurality of electronic circuit devices, such as semiconductor packages, semiconductor dies, and/or passive elements. These electronic circuit devices and a portion of the PCB are often covered or encapsulated by an encapsulant material. The PCB also includes a plurality of input/output (I/O) pads disposed on the side or surface thereof opposite that having the electronic circuit devices thereon. These I/O pads are not covered by the encapsulant material, and thus are exposed in the completed module which comprises the PCB, the electronic circuit devices and the encapsulant material. In certain memory card designs, the completed module is inserted into a complementary cavity formed within a case of the memory card, such case generally defining the outer appearance of the memory card. The module is secured within the cavity of the case through the use of an adhesive such that the I/O pads disposed on the PCB are not covered by the case, and thus remain exposed in the fully assembled memory card. These I/O pads of the memory card provide an external interface for an insertion point or socket. The completed memory card has a generally rectangular configuration, with most memory cards including a chamfer formed at one edge thereof which is adjacent to the I/O pads.
The above-described module typically has a generally quadrangular configuration, with the cavity formed in the case also having a generally quadrangular configuration corresponding to the shape of the module. As a result, in order to smoothly guide and insert the module into the cavity in the case, it is typically necessary to size the cavity relative to the case such that a sufficient tolerance or clearance is provided between the side surfaces of the module and the internal side walls of the cavity in the case. More particularly, in order to smoothly guide and insert the module into the cavity, a gap of at least 0.15 millimeters is typically needed between each side surface of the module and the corresponding internal side wall of the cavity. However, when a gap of the required size or width of about 0.15 millimeters is defined between each side surface of the module and the corresponding internal side wall of the cavity, adhesive applied between the top surface of the module and the internal top wall of the cavity typically flows through such gaps and drains out of the cavity to the bottom surface of the case. As will be recognized, the adhesive leaking from within the cavity contaminates the outside of the memory card. In addition, since a mounting error of at least 0.15 millimeters may occur when the module is fixed within the cavity, the positions of the I/O pads of the PCB are variable. In this regard, there is a possibility that an ESC (electrostatic current) pad may not meet a required regulation. Further, if the module is deflected to one side of the cavity, a gap of about 0.30 millimeters may be formed at the opposite side of the cavity, thus creating a gap that is visible to the naked eye and deteriorates from the external appearance of the memory card.
The present invention addresses and overcomes these drawbacks by providing a memory card construction wherein the module of the memory card is uniquely configured to prevent adhesive leakage from within the corresponding cavity of the case of the memory card when the module is secured within the cavity. These as well as other features and advantages of the present invention will be described in more detail below.